A Triazine Derivative Usable for the Glycosylation Reaction of Unprotected Sugars

2,4-Bis(benzyloxy)-6-chloro-1,3,5-triazine (1) is one of the triazine derivatives and is efficiently used for the synthesis of unprotected glycosyl donors.¹⁾ The first report of the glycosylation of unprotected sugars was achieved by Fischer in 19th century,²⁾ but this synthetic method is limited to the use of acid-stable glycosyl donors because of the requirement for acidic conditions. On the other hand, the glycosylation of unprotected sugars using 1 can be complementarily used because the reaction proceeds under basic conditions. For instance, the reaction of 1 with unprotected sugars successfully proceeds in the presence of a base to give the 4,6-dibenzyloxy-1,3,5-triazin-2-yl (DBT) group substituted β-glycosides (2). Subsequent catalytic hydrogenation of benzyloxy groups of DBT in an excess amount of alcohol affords the corresponding alkoxy group substituted glycosides with the elimination of cyanuric acid. This glycosylation using 1 can be applied not only to monosaccharides but also unprotected polysaccharides, so that it is expected to be used in the future.